1. Field of the Invention
The present invention relates to a blower which sucks in a gas, makes the sucked in gas rise in temperature, and discharges it from a discharge port, more particularly relates to a blower for gas laser oscillator use for making a laser gas circulate inside the gas laser oscillator.
2. Description of the Related Art
A blower which sucks in a gas, makes the sucked in gas rise in temperature, and discharges it from a discharge port has been known since the past. Such a blower, as shown in Japanese Patent Publication No. 8-335731A, is used for making a laser gas circulate inside a gas laser oscillator.
FIG. 14 is a cross-sectional view showing the configuration of a conventional blower. Here, an example of an oil lubrication type of blower for gas laser oscillator use will be shown.
A blower 100 shown in FIG. 14 is provided with a gas blowing part 2 which blows gas by rotation of an impeller 1 and a motor part 3 for making the impeller 1 rotate.
A casing 4 of the gas blowing part 2 surrounds the impeller 1 and is formed integrally with a casing 5 of the motor part 3. Furthermore, the casing 4 of the gas blowing part 2 is formed with a single suction port 4a for sucking in a gas and discharge ports 4b, 4c for discharging the gas. By the impeller 1 rotating about a center axis X, the gas is sucked in from the suction port 4a as shown by the arrow 6 in the figure and is discharged from the discharge ports 4b, 4c as shown by the arrows 7, 8.
The casing 5 of the motor part 3 holds a rotor 9 for making the impeller 1 rotate. Further, the casing 5 of the motor part 3 is provided with a partition wall part 5a which partitions the space inside the casing 4 of the gas blowing part 2 from the space inside the casing 5 of the motor part 3. The center of rotation of the impeller 1 and the center of rotation of the rotor 9 are on the same center axis X. Further, at the inner circumferential surface of the casing 5 of the motor part 3, a stator 10 is set so as to surround the rotor 9. The rotor 9 can rotate by receiving electromagnetic force from the stator 10.
In an oil lubrication type of blower 100, the rotor 9 is arranged in the vertical direction. Further, at the inside bottom part of the casing 5 of the motor part 3, an oil reservoir 14 which stores the lubricating oil is formed.
Inside the oil reservoir 14, a bearing part 11 is arranged for supporting a bottom end part 9a of the rotor 9 in the axial direction to be able to rotate and so that it is immersed in the oil. On the other hand, a top end part 9b of the rotor 9 in the axial direction passes through the partition wall part 5a and sticks out inside the gas blowing part 2. Further, the top end part 9b of the rotor 9 in the axial direction is coupled with a center of rotation part of the impeller 1.
The partition wall part 5a is formed with a through hole through which the top end part 9b of the rotor 9 in the axial direction passes. A bearing part 12 is arranged in the through hole. The top end part 9b of the rotor 9 in the axial direction is supported at the bearing part 12 to be able to rotate.
Further, the rotor 9 is designed to utilize a centrifugal force accompanying the high speed rotation of the rotor 9 to be able to supply part of the oil of the oil reservoir 14 to the bearing part 12. The supplied oil is used for lubricating the bearing part 12 and then is returned to the oil reservoir 14.
Further, at the through hole of the partition wall part 5a through which the top end part 9b of the rotor 9 in the axial direction passes, a shaft seal 13 is arranged to adjoin the bearing part 12. Due to this, it becomes difficult for the oil which is supplied to the bearing part 12 to enter the casing 4 of the gas blowing part 2.
However, the top end part 9b of the rotor 9 in the axial direction is the high speed rotating shaft part, so as the shaft seal 13, to not interfere with high speed rotation of the shaft part, a noncontact type shaft seal, for example, a labyrinth seal, is employed.
Furthermore, to prevent the oil from entering the inside of the gas blowing part 2 from the motor part 3, the casing 5 of the motor part 3 is formed with an exhaust port 5b. By constantly evacuating the inside space of the casing 5 of the motor part 3 from the exhaust port 5b, the pressure inside of the motor part 3 is made lower than the pressure inside the gas blowing part 2. Due to this, the oil inside the motor part 3 is kept from entering the inside of the gas blowing part 2 and being dispersed by the impeller 1 inside the gas laser oscillator.
As explained above, in the conventional blower 100, a noncontact type shaft seal 13 is arranged in the clearance between the outer circumferential surface of the top end part 9b of the rotor 9 in the axial direction and the inner circumferential surface of the through hole through which this top end part 9b passes. Furthermore, the inside space of the casing 5 of the motor part 3 is evacuated. For this reason, part of the gas inside the gas blowing part 2 is sucked into the casing 5 of the motor part 3; therefore, a flow of gas is created from the gas blowing part 2 to the inside of the motor part 3. If a flow of gas 15 to the inside of the motor part 3 is created, this flow of gas 15 is liable to cause the particle-like foreign matter 16 to reach the shaft seal 13.
FIG. 15 is a cross-sectional view of the surroundings of the shaft seal 13 in the conventional blower 100 and schematically shows the state where the foreign matter 16 reaches the shaft seal 13.
As shown in FIG. 15, the noncontact type shaft seal 13 has a rotating part 13a which rotates along with the rotation of the rotor 9 and a fixed part 13b which does not rotate. There is a clearance between the rotating part 13a and the fixed part 13b. However, that clearance is made as small as possible so as to secure an oil sealing ability. For this reason, the foreign matter 16 is liable to reach the shaft seal 13, the foreign matter 16 is liable to end up being caught in the clearance present at the shaft seal 13, and the shaft seal 13 is liable to seize and be damaged.